Light sensor with voltage reversing mechanism detecting light from an ambient light source and a light emitting component

Abstract

A light sensor having a voltage reversing mechanism is provided. A photoelectric component converts a first light signal into a first photocurrent. A capacitor is charged to a first voltage by the first photocurrent. A counter counts a first coarse count value according to the first voltage. The photoelectric component converts a second light signal into a second photocurrent. The capacitor is charged from a reversed first voltage to a second voltage by the second photocurrent. The counter counts a second coarse count value according to the second voltage. The counter counts a fine count value according to the second coarse count value. One of the first light signal and the second light signal is emitted by both of an ambient light source and a light-emitting component and then reflected by a tested object, and the other one of them is emitted by only the ambient light source.

What is claimed is: 
     
       1. A light sensor having a voltage reversing mechanism, comprising:
 a photoelectric component configured to convert light energy of a first light signal into a first photocurrent and then to provide the first photocurrent to a capacitor to charge the capacitor to a first voltage; 
 a voltage reversing circuit connected to the capacitor and configured to reverse the first voltage to form a reverse voltage; 
 a comparator, wherein a first input terminal of the comparator is connected to the capacitor, a second input terminal of the comparator is coupled to a reference voltage, and the comparator is configured to compare the first voltage with the reference voltage to output a first comparing signal; and 
 a counter, wherein an input terminal of the counter is connected to an output terminal of the comparator, and the counter is configured to count a first coarse count value according to the first comparing signal; 
 wherein, after the first coarse count value is counted, the photoelectric component converts light energy of a second light signal into a second photocurrent and provides the second photocurrent to the capacitor to charge the capacitor to a second voltage from the reverse voltage; 
 wherein, the comparator compares the second voltage with the reference voltage to output a second comparing signal, and the counter counts a second coarse count value according to the second comparing signal; 
 wherein, after the second coarse count value is counted, the counter performs a fine counting operation on the second coarse count value to count a fine count value; 
 wherein, one of the first light signal and the second light signal is a light signal that is emitted by both of a light-emitting component and an ambient light source and then is reflected by a tested object, and the other one of the first light signal and the second light signal is a light signal that is emitted by only the ambient light source. 
 
     
     
       2. The light sensor according to  claim 1 , wherein the voltage reversing circuit reverses the first voltage that is a positive voltage to form the reverse voltage that is a negative voltage, and an absolute value of the reverse voltage is equal to the first voltage. 
     
     
       3. The light sensor according to  claim 1 , wherein the capacitor is charged to the second voltage that is a positive value from the reverse voltage that is a negative voltage, by the second photocurrent. 
     
     
       4. The light sensor according to  claim 1 , wherein, when the light energy of the light signal emitted by only the ambient light source is larger than an energy threshold, the counter counts the first coarse count value according to the light signal that is emitted by both of the light-emitting component and the ambient light source and then is reflected by the tested object, within a first phase time;
 wherein, after the first phase time ends, the counter counts the second coarse count value according to the light signal emitted by only the ambient light source, within a second phase time. 
 
     
     
       5. The light sensor according to  claim 1 , wherein, when the light energy of the light signal emitted by only the ambient light source is smaller than an energy threshold, the counter counts the first coarse count value according to the light signal emitted by only the ambient light source, within a first phase time;
 wherein, after the first phase time ends, the counter counts the second coarse count value according to the light signal that is emitted by both of the light-emitting component and the ambient light source and then is reflected by the tested object, within a second phase time. 
 
     
     
       6. The light sensor according to  claim 1 , further comprising:
 a current supplying component connected to the capacitor, and configured to supply a bias current to the capacitor to charge the capacitor when the photoelectric component provides the second photocurrent to the capacitor. 
 
     
     
       7. The light sensor according to  claim 6 , wherein the current supplying component provides the bias current to the capacitor to charge the capacitor when the photoelectric component provides the first photocurrent to the capacitor. 
     
     
       8. The light sensor according to  claim 6 , wherein, when the light energy of the light signal emitted by only the ambient light source is smaller than an energy threshold, the current supplying component provides the bias current to the capacitor to charge the capacitor. 
     
     
       9. The light sensor according to  claim 6 , wherein the current supplying component includes a current source. 
     
     
       10. The light sensor according to  claim 1 , further comprising:
 a current amplifier connected to the photoelectric component and the capacitor, and configured to amplify the second photocurrent and then to provide the second photocurrent amplified to the capacitor to charge the capacitor. 
 
     
     
       11. The light sensor according to  claim 10 , wherein the current amplifier is configured to amplify the first photocurrent and then to provide the first photocurrent amplified to the capacitor to charge the capacitor. 
     
     
       12. The light sensor according to  claim 1 , wherein the voltage reversing circuit includes:
 a first switch component, wherein a first terminal of the first switch component is connected to the photoelectric component and the first input terminal of the comparator, and a second terminal of the first switch component is connected to a first terminal of the capacitor; 
 a second switch component, wherein a first terminal of the second switch component is connected to a second terminal of the capacitor, and a second terminal of the second switch component is grounded; 
 a third switch component, wherein a first terminal of the third switch component is connected to the photoelectric component and the first input terminal of the comparator, and a second terminal of the third switch component is connected to the second terminal of the capacitor; and 
 a fourth switch component, wherein a first terminal of the fourth switch component is connected to the first terminal of the capacitor, and a second terminal of the fourth switch component is grounded; 
 wherein, when the first switch component and the second switch component are turned on, the capacitor is charged to the first voltage; 
 wherein, when the third switch component and the fourth switch component are turned on, the capacitor is charged to the second voltage from the reverse voltage of the first voltage.